New PCM questions [Archive] - Forum


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04-22-2008, 05:14 AM
2 Questions

I put my new PCM in and i think i need to put the old one back in. I wanted to know if i put the old one back in, do i have to do the Crankcase position sensor learn or will it already know?

The reason why i am taking it out is becasue my tranny isnt liking the shift kit. I have about a 2-3 second delay in between first and second gear and it is killing my 1/4 mile times. Can I somehow reprogram the new pcm to take the shift kit out so that i can still use all of the other good features?


04-22-2008, 06:04 AM
I hate to say this but the problem is your trans... not the PCM programming. There are tons of members here who have the EXACT same settings applied to their PCMs without any type of "issue"

in any case.. yes you can replace the new pcm with your old without having to do a case learn or security learn...

I would highly suggest having the 1-2 shift solenoid looked at and possibly replaced as it is a common issue with the older 4t45e/4t40e... GM went to a new 1-2 solenoid design as a result of this issue.

the issue may also be that you have a hairline crack in 1 of your rubber accumulator pistons (also a common issue in older transmissions)

also if you really wanted to I can certainly remove the shift kit setting fromt he PCM but I really dont see how this would be advantageous for you since the problem is mechanical...

04-22-2008, 06:11 AM
x2 on what Mark said, the higher line pressure or whatever is done on the aftermarket PCMs to quicken up shifts, will bring out the accumulator piston / 1-2 shift solenoid problem quickly. I don't remember if there's a TSB on it but plenty have had the issue, might want to read around on the fix there was one good thread I recall

04-22-2008, 06:26 AM
here are a few threads i just dug up really quick...